Department of Earth and Environmental Sciences, Korea University, Seoul, South Korea.
Biosciences Division, Argonne National Laboratory, Lemont, IL, 60439, USA.
J Environ Manage. 2021 Aug 15;292:112756. doi: 10.1016/j.jenvman.2021.112756. Epub 2021 May 25.
Urban subsurface environments are often different from undisturbed subsurface environments due to the impacts of human activities. For example, deterioration of underground infrastructure can introduce elevated levels of Ca, Fe, and heavy metals into subsurface soils and groundwater. Likewise, leakage from sewer systems can lead to contamination by organic C, N, S, and P. However, the impact of these organic and inorganic compounds on biogeochemical processes including microbial redox reactions, mineral transformations, and microbial community transitions in urban subsurface environments is poorly understood. Here we conducted a microcosm experiment with soil samples from an urban construction site to investigate the possible biotic and abiotic processes impacted when sulfate and acetate or lactate were introduced into an urban subsurface environment. In the top-layer soil (0-0.3 m) microcosms, which were highly alkaline (pH > 10), the major impact was on abiotic processes such as secondary mineral precipitation. In the mid-layer (2-3 m) soil microcosms, the rate of Fe(III)-reduction and the amount of Fe(II) produced were greatly impacted by the specific organic acid added, and sulfate-reduction was not observed until after Fe(III)-reduction was complete. Near the end of the incubation, some genera related to syntrophic acetate oxidation and methanogenesis were observed in the lactate-amended microcosms. In the bottom-layer (7-8 m) soil microcosms, the rate of Fe(III)-reduction and the amount of Fe(II) produced were affected by the concentration of amended sulfate. Sulfate-reduction was concurrent with Fe(III)-reduction, suggesting that Fe(II) production was likely due to abiotic reduction of Fe(III) by sulfide produced by microbial sulfate reduction. The slightly acidic initial pH (5.8) of the mid-soil system was a major factor controlling sequential microbial Fe(III) and sulfate reduction versus parallel Fe(III) and sulfate reduction in the bottom soil system, which had a neutral initial pH (7.2). 16S rRNA gene-based community analysis revealed a variety of indigenous microbial groups including alkaliphiles, dissimilatory iron and sulfate reducers, syntrophes, and methanogens tightly coupled with, and impacted by, these complex abiotic and biogeochemical processes occurring in urban subsurface environments.
城市地下环境通常与未受干扰的地下环境不同，因为人类活动的影响。例如，地下基础设施的恶化会将 Ca、Fe 和重金属等大量元素引入地下土壤和地下水中。同样，污水系统的泄漏会导致有机 C、N、S 和 P 的污染。然而，这些有机和无机化合物对城市地下环境中微生物氧化还原反应、矿物转化和微生物群落演替等生物地球化学过程的影响知之甚少。在这里，我们进行了一项微宇宙实验，使用来自城市建筑工地的土壤样本，研究了当硫酸盐和乙酸盐或乳酸盐被引入城市地下环境时，可能会对生物和非生物过程产生影响。在高度碱性（pH>10）的上层土壤（0-0.3 m）微宇宙中，主要影响是非生物过程，如次生矿物沉淀。在中层（2-3 m）土壤微宇宙中，添加的特定有机酸极大地影响了 Fe(III)-还原的速率和产生的 Fe(II)量，直到 Fe(III)-还原完成后才观察到硫酸盐还原。在培养接近尾声时，在添加乳酸盐的微宇宙中观察到一些与协同乙酸氧化和产甲烷有关的属。在底层土壤（7-8 m）微宇宙中，Fe(III)-还原的速率和产生的 Fe(II)量受添加硫酸盐浓度的影响。硫酸盐还原与 Fe(III)-还原同时发生，表明 Fe(II)的产生可能是由于微生物硫酸盐还原产生的硫化物对 Fe(III)的非生物还原。中层土壤系统初始 pH 值略酸性（约 5.8）是控制顺序微生物 Fe(III)和硫酸盐还原与底层土壤系统平行 Fe(III)和硫酸盐还原的主要因素，该系统初始 pH 值中性（约 7.2）。基于 16S rRNA 基因的群落分析揭示了各种土著微生物群体，包括嗜碱微生物、异化铁和硫酸盐还原菌、共栖体和产甲烷菌，它们与发生在城市地下环境中的这些复杂的非生物和生物地球化学过程紧密耦合，并受到这些过程的影响。
